Zenone et al. Helgol Mar Res (2016) 70:21 DOI 10.1186/s10152-016-0472-9 Helgoland Marine Research

SHORT COMMUNICATION Open Access Substrate preference and settlement behaviour of the megalopa of the invasive gibbesi (, Percnidae) in the Mediterranean Sea Arturo Zenone1, Fabio Badalamenti1, Vincenzo M. Giacalone2, Luigi Musco1,3, Carlo Pipitone1* , Tomás Vega Fernández1,3 and Giovanni D’Anna1

Abstract The transition from a planktonic to a benthic life is a critical phase in which sub-adults are particularly exposed to the risk of predation and dispersion into unsuitable habitats, and plays a crucial role in the distribution, structure and dynamics of marine populations. Settlement involves the selection of an adequate substrate that provides shelter and food during early life stages. Percnon gibbesi is an alien brachyuran crab that has invaded the Mediterranean, where it is preferentially associated to boulders covered with shallow algal turf. The mechanisms of substrate selection leading to the settlement of megalopae are still unknown in P. gibbesi, yet their knowledge may shed light on its high inva- siveness. We examined the substrate preference and settlement behaviour of 36 megalopae of P. gibbesi using three natural substrates in an experimental mesocosm: gravel, cobbles and flat stones. Video recordings of 30-min trials were used to assess the substrate preference, measure the time to selection and observe the behaviour of the mega- lopae. Strong preference was given to hard and stable substrates i.e., cobbles and flat stones with interstices where to hide, which are also the most suitable as they provide shelter and food. Direct selection was the dominant behaviour followed by exploration and lastly by hesitation. The megalopae selected quickly the most suitable substrate to settle, likely enhancing their chances of survival. Our findings suggest that rapid settlement on a suitable substrate contrib- utes to the success of the biological invasion of P. gibbesi along the Mediterranean coasts. Keywords: Microhabitat, Larval stage, Brachyuran , Light traps, Alien species

Background transition from planktonic to benthic life (i.e., the settle- Settlement and recruitment of marine organisms are ment) is a critical step in the life cycle of benthic inverte- complex processes affected by many biotic (larval mor- brates that have a planktonic larva [4]. Two phases may phology, pelagic phase duration, behaviour, etc.) and be distinguished in this process: (1) a behavioural phase abiotic (oceanographic features, habitat structure, etc.) of search for a suitable substrate that provides shelter and factors that occur at different temporal and spatial scales food, and (2) a phase of permanent residence or attach- [1]. Many marine benthic organisms have a planktonic ment to the substrate, which triggers the metamorpho- larval phase as part of their reproductive and disper- sis [1]. The ability of recognizing a suitable substrate is sal strategy [2] that may disperse over large areas before therefore essential to enhance the survival chances of set- settling and recruiting in a suitable habitat [3]. The tlers and to guarantee the success of recruitment, and it ultimately determines distribution, structure and dynam- ics of populations. *Correspondence: [email protected] 1 CNR-IAMC, Castellammare del Golfo ‑ Via G. da Verrazzano 17, Like most benthic marine organisms, brachyuran crabs 91014 Castellammare del Golfo, Italy have a pelagic larval phase followed by a benthic phase Full list of author information is available at the end of the article

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